1. Field of the Invention
The present invention relates to an eye refractive power measurement apparatus which objectively measures a refractive power of an eye to be examined.
2. Description of Related Art
It is conventionally known an eye refractive power measurement apparatus which projects a target for measurement onto a fundus of an eye to be examined and objectively measures a refractive power of the eye based on the reflected light therefrom. When precisely measuring a refractive power of the eye using this kind of apparatus, the measurement is carried out usually by relaxing accommodation of the eye by a fogging mechanism and the measurement is repeated a plurality of times. Statistical processes are given to the measurement results obtained thereby such as letting the median or the average be the typical value of the all data values indicating the eye refractive power. The value obtained through the statistical processes is utilized as an initial value in a subjective measurement to be performed next.
However, when measuring an eye which has low hyperopia, an examinee looks into the apparatus and thus so-called instrumental myopia is often caused. As a result, the accommodation of the eye is likely to be unstable. Owing to the unstableness of the accommodation, it may be the case where all the measurement results indicate a negative (or minus) spherical power, or only one result out of three indicates a positive (or plus) spherical power. Upon these cases, if decided in the aforementioned way, the typical value will be of a negative power. Judging from this typical value, an examiner may diagnose that the eye as myopia. If a subjective refractive power measurement is started from a negative spherical power, with a continues accommodation, it is extremely difficult to obtain corrective spherical value for the hyperopic eye by relaxing the accommodation.